The present invention relates to a circuit arrangement for a telecommunication exchange which may be a private branch exchange system. The local exchange typically has a centrally controlled switching network via which exchange, internal and enquiry calls can be set up, and in which signals, d.c. biases and the like can be applied to the switching network, and in which the exchange trunks are connected via amplifiers to the inlets of a first connecting stage of the switching network.
If, in a telephone private branch exchange system, a subscriber making an exchange call makes an enquiry call to another subscriber of the private branch exchange system, the switching network must be terminated toward the exchange trunk during the enquiry call. To do this, the amplifier connecting the exchange trunk to the occupied input of the private branch exchange must be inactivated and the exchange trunk must be terminated in a resistance whose value is specified by the company or authority operating the communications network. It is known to effect this termination with special switching devices provided on the public-exchange side of the amplifier, such special switching devices being necessary for each exchange trunk.